| With the rapid increase of population quantity and industrial energy consumption,environmental pollution and energy shortage phenomenon is highlighted,and it is imperative to develop the new biodegradable multi-functional materials.As the product of low grade weathered coal,Nano humic acid(NHA)has more active group on the molecular chain and unique excellent performance.But it also has some insufficient on the acid resistance and swelling ability,which is necessary to be modified.Under the action of initiator,NHA can react with unsaturated olefin monomers which will change the molecular structure,the practical performance of NHA will be significantly improved.In this paper,NHA-GO and the composite material of NHA-GO-polyaniline(PANI)were prepared based on NHA and GO,and the preparation methods and technological conditions as well as thermodynamic property of NHA were investigated,meanwhile the adsorption and electrochemical properties of two new composite materials were also studied.NHA-GO composite material was prepared using NHA and GO as raw materials,N,N'-Methylenebisacrylamide as crosslinking agent,potassium peroxydisulfate as initiator.Based on the the single factor experiment results and through response surface methodology,the optimal preparation conditions were as follows: reaction temperature 51.2 °C,substrate ratio 9.2 : 1,crosslinking agent dosage 12.60 wt.%,and initiator dosage 249 mg·L-1,and the swelling ratio could reach 92.2% at these conditions.The physical and chemical properties of the composite material were characterized by AFM,SEM,FTIR,TG-DTG,XRD,XPS and so on.The results showed that: the composite material had uneven surface structure and network and the bridge structure in three dimensional space.What's more,it had more functional groups and active sites as well as better thermal stability.The solubility data of NHA in different solvents and methanol-ethanol mixture with different ratios within the temperature range of 283.15~303.15 K was got by balance method.The equation of Van't Hoff,Apelblat and ?h were employed to correlate the solubility data,and the results showed that Apelblat equation was obviously better than Hoff and ?h equation.Standard solution entropy and standard enthalpy of dissolution were got through Van't Hoff equation,which confirmed that the dissolution process is spontaneous and entropy driven.The solubility data in different solvents and methanol-ethanol mixture with different ratios were compared using Hildebrand solubility principle.The pyrolysis process and kinetic equation was studied,and the results showed that,pyrolysis mechanism function was G(?)=[1-(1-?)1/3]1/2(?=0.035–0.97),f(?)=6[1-(1-?)1/3]1/2(1-?)2/3,which was two-order reaction;kinetic equation was d?/dt=3.54×1017exp(-210.83/8.314T)6[1-(1-?)1/3]1/2(1-?)2/3,and thermodynamic data of ?~H?,?~S?and ?G~? were got.Using NHA-GO as adsorbent,the influence of different factors on adsorbing aniline and 4-chlorophenol was investigated through static experimental system.The results showed that,with the increase of solution pH,the equilibrium adsorption capacity of aniline and 4-chlorophenol were both decreased;The presence of salt ions was helpful for the adsorption of aniline but limited the adsorption of 4-chlorophenol.The thermodynamics,kinetics,mechanism and regeneration performance of aniline and 4-chlorophenol with NHA-GO in aqueous solution were investigated.The results showed that Langmuir and Redlich-Peterson(R-P)model could describe the adsorption behavior of aniline and 4-chlorophenol respectively,the adsorption of aniline was spontaneous and endothermic,and the adsorption of 4-chlorophenol was endothermic and the entropy were increasing.The adsorption kinetics followed the pseudo two order and Elovich adsorption rate model,which was mainly chemical adsorption.The adsorption of aniline was controlled by liquid film diffusion,whereas the adsorption of 4-chlorophenol was controlled by liquid film diffusion and intraparticle diffusion.The adsorption mechanism was mainly dependent on hydrogen bonding and electrostatic adsorption,and the effects of ethanol and 0.1M HNO3 on the de-sorption of aniline and 4-chlorophenol were better.The activation energy for adsorption of aniline and 4-chlorophenol was calculated.Based on dynamic column adsorption technology,the influence of different factors such as material flow rate,initial concentration,bed height and adsorption temperature on the dynamic adsorption of aniline on the composite were investigated systematically.The experiments showed that,the optimal conditions for the adsorption of aniline were as follows: material flow rate 20 mL·min-1,initial concentration 50 mmol·L-1,bed height 20 mm,adsorption temperature 298.15 K,and 2 adsorption columns.Based on the mathematical model of dynamic adsorption and the formula of breakthrough curve,we could find that the experimental and predicted values were in good agreement,which could provide theoretical basis for the design and process optimization of the same column.NHA/PANI/GO composites were prepared by in-situ chemical oxidative polymerization,and the optimal conditions were as follows: reaction time 16 h,reaction temperature 10°C,particle size of NHA 60 nm,mass ratio of NHA to GO 1:0.9(g:mg),mass ratio of PANI to GO 1:3,the specific capacitance value 710 F·g-1.The characterization results of the composites by AFM,FTIR,SEM and XPS showed that,GO acted as a conductive skeleton,which could rapidly promote charge transfer and effectively control NHA particle volume change,and increased electrode stability;The interfacial properties of NHA particles and GO can be controlled by Polyaniline,which could make the ions diffuse freely between NHA particles and GO;The nano effect of NHA particles can shorten the length of lithium ion transfer and improve the kinetics of lithium intercalation reaction.The electrochemical behavior of the composites in three electrode system was studied,which showed that,the specific capacitance was 641 F g-1 when current density was 5.0 A g-1,what's more,the specific capacitance still kept 630~740 F g-1 after recycling for 4000 times,and the retention rate could reach 86%,which could supply data guideance for carrying out large scale application. |
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